A crisp black-and-white scan can omit a pale pencil note that was visible on the paper. It may also lose information carried by coloured highlighting. The correct scan mode depends on what the document needs to preserve, not just whether most of its text is black.

Make the faint detail the test target

Select a page containing the lightest important mark. Note its position on the original so you can find it in each sample. If colours distinguish approvals, changes or categories, include that feature in the test as well.

Start with a colour scan when colour itself matters. For a monochrome original, compare greyscale with the scanner's black-and-white mode while keeping resolution and page area the same. Open the saved files instead of relying solely on the small preview.

Epson's Scan 2 troubleshooting guidance identifies the Threshold control for black-and-white images and suggests greyscale as another option. It also describes text, background and noise adjustments where available. These controls depend on the scanner and current settings; their presence is not a reason to enable all of them together.

Change one control and inspect the whole page

If testing a threshold or text enhancement adjustment, make one change and rescan. Check both the faint note and dense printed text. An adjustment that reveals the note might also fill the centres of small letters or exaggerate background marks.

Do not erase useful evidence merely to obtain a cleaner-looking white background. For receipts, forms or handwritten records, completeness can matter more than a visually tidy image. Keep an unenhanced version when the source has subtle or ambiguous markings.

Once the sample passes, use the accepted preset for similar pages and inspect exceptions separately. A setting suitable for dark typed sheets may fail on a pale carbon copy in the same bundle. Preserve the original paper until you have checked that all required information survived the saved scan.

Sources: Epson Scan 2 character-quality controls.